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Chapter 3:
Prenatal Development
and Birth
IN THIS CHAPTER
• Conception and Genetics
• Genetic and Chromosomal Disorders
• Pregnancy and Prenatal
Development
• Problems In Prenatal Development
• Birth and The Neonate
LEARNING OBJECTIVES
3.1 What are the characteristics of the zygote?
3.2 In what ways do genes influence development?
3.3 What are the effects of the major dominant, recessive,
and sex-linked diseases?
3.4 How do trisomes and other disorders of the autosomes
and sex chromosomes affect development?
3.5 What are the characteristics of each trimester of
pregnancy?
3.6 What happens in each stage of prenatal development?
3.7 How do male and female fetuses differ?
3.8 What behaviors have scientists observed in fetuses?
3.9 How do teratogens affect prenatal development?
LEARNING OBJECTIVES (con’t)
3.10 What are the potential adverse effects of tobacco,
alcohol, and other drugs on prenatal development?
3.11 What risks are associated with teratogenic maternal
diseases?
3.12 What other maternal factors influence prenatal
development?
3.13 How do physicians assess and manage fetal health?
3.14 What kinds of birth choices are available to expectant
parents?
3.15 What happens in each of the three stages of labor?
3.16 What do physicians learn about a newborn from the
Apgar and Brazelton scales?
3.17 Which infants are categorized as low birth weight, and
what risks are associated with this status?
CONCEPTION AND GENETICS
Chromosomes, DNA, and Genes
Process of Conception
 Ovum
 Sperm
 Zygote
Chromosomes
 DNA
 Genes
CONCEPTION AND GENETICS
Sex Determination
Chromosomes
 Autosomes
 Sex chromosomes (X, Y)
Chromosomal Differences
 Androgens and SRY gene
 Sex chromosomes (X, Y)
 Gonad development
CONCEPTION AND GENETICS
Multiple Births
Twins
• Identical (monozygotic)
• Fraternal (dizygotic)
• Semi-identical (different genes from father)
STOP AND THINK!
Your textbook notes an increase in multiple births
over the past thirty years.
Why has this occurred?
CONCEPTION AND GENETICS
How Genes Influence Development
Genotype: genetic blueprint
Phenotype: observable characteristics
• Dominant–recessive pattern
• Polygenic inheritance
Twins in Genetic Research
Comparison of identical and fraternal twins has been
been used for many decades to exam the role of
heredity in human development.
Identical twins are more similar than fraternal twins on
measures of emotionality, activity, sociability, and
intelligence
Yet correlations that twins researchers have found are
less than +1.00, even for identical twins who grow up in
the same home.
This offers strong evidence that psychological traits are
clearly influenced by heredity. This might not be true for
physical traits.
Can you apply this information?
Critical Analysis
1. Fraternal twins are no more genetically similar
than non-twin siblings, yet the IQs of fraternal twins
are more strongly correlated than those of non-twin
brothers and sisters. What explanations can you
think of to explain this difference?
2. The term environment is extremely broad. What
are some of the individual variables that comprise
an individual’s environment?
LET’S TAKE A LOOK…
Whose hair do you have?
On the next slide you will see the genetics of hair
type. Did you answer the above question correctly?
THE GENETICS OF HAIR TYPE
GENETIC SOURCES OF NORMAL TRAITS
CONCEPTION AND GENETICS
Other Types of Inheritance
• Genomic imprinting: some genes
biochemically marked at time ova and sperm
develop
• Mitochondrial inheritance: genes in
mitochondria
CONCEPTION AND GENETICS
Multi-Factorial Inheritance (MFI)
MFI: inheritance affected by genes and
environment
• Five general principles (Rutter et al.)
In what ways have genetics and environment
integrated to influence your development?
GENETIC DISORDERS
Autosomal Disorders
Autosomal gene: one of twenty-two pairs of
autosomes that are involved in sex determination
Autosomal recessive disorder: two copies of the
abnormal gene must be present for the disease or
trait to develop.
Autosomal dominant disorder: abnormal gene
from one parent sufficient to inherit disease or trait
See Table 3.2 (p. 55) for a summary of some
genetic disorders.
SOME GENETIC DISORDERS
SEX-LINKED INHERITANCE
GENETIC DISORDERS
Sex-Linked Disorders
Sex-linked disorders: caused by recessive gene
on X chromosome
Red–Green Colorblindness
Hemophilia
Fragile X Syndrome
STOP AND THINK…
Why do boys have Fragile X Syndrome more often
than girls do?
CHROMOSOMAL ERRORS
Trisomies and Monosomies
Trisomies: three chromosomes, rather than the
usual pair
Monosomies: absence of one member of
chromosome pair
CHROMOSOMAL ERRORS
Sex Chromosome Anomalies
•
•
•
•
•
Trisomy 21: Down syndrome
XXY: Klinefelter’s syndrome
XO: Turner’s syndrome
XXX: girls with an extra X
XYY: boys with an extra Y
PREGNANCY AND PRENATAL DEVELOPMENT
The Mother’s Experience: First Trimester
Zygote implants in
the uterus
Cervix thickens and
secretes mucus to
protect embryo
Uterus shifts and
puts pressure on
bladder
Care
• Regular prenatal care critical at this time
Problems
• Ectopic pregnancy, bleeding, miscarriage
Missed period
Breast enlargement
PREGNANCY AND PRENATAL DEVELOPMENT
The Mother’s Experience: Second Trimester
Weight gain
“Showing”
Fetal
movements felt
Increased
appetite
Care
 Monthly doctor visits continue
 Ultrasound
Problems
 Gestational diabetes; Rh incompatibility; increased
blood pressure
 Miscarriage; premature labor
PREGNANCY AND PRENATAL DEVELOPMENT
The Mother’s Experience: Third Trimester
Colostrum in
preparation for nursing
Emotional connection
between mother and
baby grows
Fetal hiccups and
thumb-sucking visible
on sonogram
Fetus has regular
activity and rest
periods
Care
Weekly visits (beginning in 32nd week)
Ultrasound to assess position; pelvic exam to check cervical
dilation
Problems
 Increased blood pressure, bleeding, bladder infection
 Premature labor
PREGNANCY AND PRENATAL DEVELOPMENT
The Prenatal Experience: Germinal Stage
Conception to Implantation
• Blastocyst implants
• Specialization of cells needed to support
development
PREGNANCY AND PRENATAL DEVELOPMENT
The Prenatal Experience: Embryonic Stage
2 to 8 Weeks after Conception
• Neural tube develops.
• Forms foundations of all body organs and
systems
• Many organs and systems begin to function.
PREGNANCY AND PRENATAL DEVELOPMENT
The Prenatal Experience: Fetal Stage
End of Week 8 until Birth
• Growth from 1/4 ounce and 1 inch to 7 pounds
and 20 inches in length
• Refinement of all organ systems
• Neuronal proliferation
• Viable at Week 24; full-term at Week 37
PARTS OF THE NEURON
Structure of a Single
Neuron
• Cell bodies first to
develop (weeks 12–24).
• Axons and dendrites
develop later (especially
final 12 weeks).
• Axons continue to
increase in size and
complexity after birth.
Figure 3.3. Parts of the Neuron
FETAL DEVELOPMENT
Figure 3.4 Fetal yawning
appears between the 10th
and 15th week. Its presence
signals the beginning of
sleep stages in the fetal
brain.
Figure 3.5 Glial cells that
develop during the last few
months of prenatal
development hold neurons
together and give form and
structure to the fetal brain.
(Source: Brown, Estroff, & Barnenott, 2004.)
PRENATAL SEX DIFFERENCES
Males
 More physically active
 Higher rates of miscarriage
 More vulnerable to prenatal problems
Females
 More sensitive to external stimulation
 More rapid skeletal development
PRENATAL SEX DIFFERENCES
Some researchers suggest:
Other researchers contend:
Males
• More physically active
• More vulnerable to
prenatal problems
Females
• More sensitive to external
stimulation
• More rapid skeletal
development
Sex differences in:
• Prenatal hormones linked
to cross-gender variations
• Prenatal problems
Can you guess what these
might be?
PRENATAL BEHAVIOR
Introducing the Amazing Fetus!
• Fetuses can differentiate between familiar and
novel stimuli by 32 to 33 weeks.
• Newborns can remember prenatal stimuli and
react accordingly.
• Very active fetuses tend to be active children
who can be labeled “hyperactive” later on.
PROBLEMS IN PRENATAL DEVELOPMENT
TERATOGENS
See Figure 3.7 for
timing of
exposure
Teratogen:
substance that can
damage embryo
Greatest damage
during organ
system’s most rapid
development
THE TIMING OF TERATOGEN EXPOSURE
PROBLEMS IN PRENATAL DEVELOPMENT
Teratogens: Maternal Diseases
•
•
•
•
•
•
•
Cancer
Toxoplasmosis
Chicken pox
Parvovirus
Hepatitis B
Chlamydia
Tuberculosis
PROBLEMS IN PRENATAL DEVELOPMENT
Teratogens: Drugs
•
•
•
•
•
•
Inhalants
Accutane/vitamin A
Streptomycin
Penicillin
Tetracycline
Diet pills
PROBLEMS IN PRENATAL DEVELOPMENT
Teratogens: Drugs
•
•
•
•
•
•
Prescription
Over-the-counter drugs
Marijuana, methamphetamine, and heroin
Cocaine
Tobacco
Alcohol
PROBLEMS IN PRENATAL DEVELOPMENT
Other Maternal Influences: Diet
• Folic acid deficiencies
• Malnutrition




Neonate low birth weight
Brain stunting
Fetal death
Mental illness in adulthood
PROBLEMS IN PRENATAL DEVELOPMENT
Other Maternal Influences: Age
• First pregnancies are occurring later—average
age is now 25.1 years.
• Women over 35 have higher risks for pregnancy
complications.
• Teenage mothers have higher risks during and
after birth.
PROBLEMS IN PRENATAL DEVELOPMENT
Other Maternal Influences: Chronic Illnesses
Kinds of Illness
• Depression
• Epilepsy
• Diabetes
• Lupus
Prevention
• Monitoring of mother and fetus necessary for
most illnesses
• Fetal–maternal specialist for high-risk patient
PROBLEMS IN PRENATAL DEVELOPMENT
Environmental Hazards
Detrimental effects of hazards may be reduced
by:
• Limiting exposure to lead and mercury
• Avoiding possible harmful chemicals
PROBLEMS IN PRENATAL DEVELOPMENT
Maternal Emotions
Maternal stress and depression are related to
higher risks for the fetus.
• Social support and counseling may help.
• Mixed information from research
FETAL ASSESSMENT AND TREATMENT
Ultrasonography
Chorionic Villus Sampling (CVS)
Amniocentesis
Alpha-Fetoprotein Blood Test
Fetoscopy
CAN YOU IDENTIFY EACH METHOD?
STOP AND THINK!
• With the advent of antiretroviral drugs, the rate of
mother-to-fetus transmission has been greatly
reduced.
Do these findings justify mandatory testing and
treatment of pregnant women who are at high risk
of having HIV/AIDS?
BIRTH AND THE NEONATE
Birth Choices
Things to Consider
• Location of birth
• Birth attendants
• Drugs during labor and delivery
• “Natural childbirth”
WANT TO MAKE A BIRTH PLAN?
How would you plan the ideal birth for yourself,
a partner, or a friend?
• Go to the link below to develop your birth plan.
• Did you include everything in your above ideal
plan?
http://www.childbirth.org/interactive/ibirthplan.html
THE PHYSICAL PROCESS OF BIRTH
Labor: An Overview
Stage 1
 Contractions
 Dilation of the cervix
Stage 2
 Actual delivery of the baby
Stage 3
 Delivery of the placenta and umbilical cord
THE THREE STAGES OF LABOR
THE THREE STAGES OF LABOR
THE PHYSICAL PROCESS OF BIRTH
Birth Complications: Cesarean Deliveries
Why are Cesarean deliveries performed?
• Fetal distress
• Breech presentation
• Birth size
• Poor progress during labor
• Mother’s health and age concerns
THE PHYSICAL PROCESS OF BIRTH
Assessing the Neonate
• Apgar scale
• Brazelton Neonatal Behavioral Assessment
Why is neonatal assessment important?
THE APGAR SCALE
ASSESSING THE NEONATE
Low-Birth-Weight Babies (LBW)
LBW: below 2,500 grams (5.5 pounds)
Preterm: mostly born before Week 38
• Small-for-date neonates
Risks
• Respiratory distress syndrome
Intervention
• Adequate parental education and support
reduces the risk of complications.
ASSESSING THE NEONATE
Do LBW babies catch up?
• Development is best assessed on an individual
basis.
• Two-thirds to three-fourths of preterm infants
catch up by school entrance.
• Lowest birth weight and earlier gestational age
are associated with long-term developmental
delays.
SINGING TO PRETERM INFANTS
The use of music by NICU staff and parents to
support the development of preterm infants is
an active area of research in the emerging field
of music therapy.
• Ate more and gained weight faster
• Discharged earlier
• Higher oxygen saturation levels
• Stronger infant–parent emotional bond
Reflection
1. How could the research on singing to preemies
be put into practice in neonatal intensive care
units in nondisruptive ways?
2. If you were responsible for helping parents of
newborns understand the value of singing to
their babies, how would you explain the relevant
research to them?
WHEN DO PRETERM INFANTS CATCH UP WITH
FULL-TERM INFANTS?
Although many premature infants catch up with
their peers by the time they go to school,
developmentalists caution that the development of
preterm children is best assessed on a case-by-case
basis.
Several factors influence development.
• Birth weight
• Gestational weight
• Parental responses
You Decide
Decide which of these two statements you most
agree with and think about how you would defend
your position:
1. Two-thirds to three-quarters of premature infants
catch up to their peers by the time they go to
school, so it’s best to adopt a “wait and see”
attitude toward your child’s development before
attempting to influence it in order to avoid
pushing the child beyond his or her limits.
You Decide
2. Both parental responses and realistic
expectations are important in parenting a child
who was born prematurely, so it’s best to do
everything possible to enhance your child’s
development without expecting him or her to
develop in exactly the same way as a child who
was born at term.